The present invention relates generally to a position indicator for rotary valve actuators, and more specifically to a position indicator which indicates when the valve is in a desired position.
It is often desirable to know the position of the closure mechanism within a valve body for determining the flow of a medium passing through the valve. This is of particular importance in systems requiring frequent and accurate adjustment of the valve's medium flow. Additionally, because valve actuators are often located in areas which are poorly lighted, it is desirable to have an indicator means which can be easily read in dark environments.
Various methods have been previously devised to provide some means of indicating the position of the valve. U.S. Pat. No. 2,959,149 to Schwenk describes an underground rotary valve having an indicating disc positioned on and arcuatly movable with the valve shaft. When one of two markings on the disk are aligned with one mark positioned on the housing itself, the position of the valve closure member may be known. Another valve described in U.S. Pat. No. 2,767,681 to Pontius includes an indicator pointer which is keyed to rotate with the valve stem by a differential gear. A corresponding indicator plate journalled on the valve stem is calibrated for indicating the open and closed positions of the valve. Another valve position indicator described in U.S. Pat. No. 2,140,934 to Dopp is formed by a vertical cut made into the side of the valve stem. The vertical position of this cut corresponds to a right angle of the flow direction within the valve body to indicate when the valve is in a closed position. Because the above position indicators require additional parts such as discs or further manufacturing such as making cuts on the valve stem or body, these indicators are both time consuming and costly to implement. Additionally, these indicators are not easily implemented on valves already in use or easily readable in poorly lighted environments.
It is, therefore, an object of the present invention to provide an inexpensive and accurate means for indicating the position of the closure mechanism within a valve arrangement.
Another object of the present invention is to provide an inexpensive and accurate position indicator which may be easily implemented on valves already in use.
Still another object of the present invention is to provide an inexpensive and accurate position indicator which is easily readable under all types of lighting conditions.
It is still another object of the present invention to provide an inexpensive and accurate position indicator which is easily replaceable upon being worn.
These and other objects are attained by providing a position indicator means having a first position indicator strip arranged on a valve actuator stem or shaft and a second position indicator strip arranged on a stationary portion of a valve body such as a bonnet pad, compression plate or actuator body. The strips are positioned such that when they are in alignment with each other, the position of the closure mechanism within the valve is in a fully closed or fully opened position or any intermediate position for which an accurate indication is desired.
The indicator strips initially comprise a single strip which is applied to both the rotor valve actuator shaft and a stationary surface when the closure mechanism is in a preferred position. After the strip is attached to the respective parts of the valve, it is severed at a point where the actuator and stationary surface meet, thereby providing accurate alignment of the two strips when the valve is in the preferred position. Depending upon the valve structure, the strips can be attached to either a top or side part of the valve actuator shaft for providing respective top or side views of the same.
The strips can be formed from a plastic, aluminum or other inexpensive material having an adhesive on one face of the strips for attaching the same to the respective parts of the valve. The other face of the strips include a longitudinal area down the middle which is bordered by contrasting areas on either side. Use of fluorescent materials for these areas may be used to further improve readability of the indicators in poorly lighted environments.
Because the strips are applied to the respective valve parts with an adhesive, they can be easily replaced by a new strip when the old strips become worn.